Which factor is crucial in determining the necessary information on the sign at a fire department connection?

The system demand pressure is crucial in determining the necessary information on the sign at a fire department connection because it indicates the amount of pressure that the fire department's apparatus will need to effectively operate within the fire protection system. This information is vital for fire service personnel to understand the specific needs of the system during emergencies to ensure they can adequately supply water to the fire suppression system.

A clearly marked fire department connection sign that includes the demand pressure helps fire fighters quickly assess if the existing pressure will satisfy the requirements of the fire protection system. This is essential for proper and effective response, particularly in high-pressure situations, so that water flow can be maximized to overcome the conditions of a fire.

While the type of materials used is important for the overall construction and durability of the system, and the location of the building can influence where connections are installed, these factors do not directly relate to the operational demands of the firefighting system as clearly as the demand pressure does. Additionally, the fire department's budget is not relevant to the actual functioning of fire service mains and appurtenances in the context of this question.